The first land-walking vertebrates may have emerged from salty estuaries | Science News

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The first land-walking vertebrates may have emerged from salty estuaries

An analysis casts doubt on views that the ancient creatures arose in freshwater

By
5:29pm, May 30, 2018
tetrapod illustration

SALTY SCENE  The planet’s earliest four-footed vertebrates called tetrapods (illustrated) lived in the brackish waters of an estuary or delta, new research suggests.

Earth’s earliest land-walking vertebrates didn’t paddle about in freshwater lakes or rivers. Instead, these four-footed creatures, which appeared about 375 million years ago, lived in the brackish waters of an estuary or delta, researchers report online May 30 in Nature.

Early tetrapods, such as Ichthyostega and Acanthostega, lived an amphibious existence between land and sea: They had feet, but also gills and tails made for swimming. A new study by paleontologist Jean Goedert of Université Lyon in France and colleagues suggests that the animals also could have tolerated rapid changes in salinity, such as is found in an estuary.

The researchers analyzed sulfur and oxygen isotopes — forms of these elements with the same number of protons, but different masses — in 51 fossilized tetrapod bones from locations in what’s now Greenland and China. Compared

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